Millions of patients face significantly higher medical bills after the country’s largest private hospital operator said it would refuse to deal with insurers that did not agree to cover a bigger portion of unexpected cost surges in the future.

Ramsay Health Care, with 70 hospitals across the country, says it has put on hold plans to build or buy any more centres, citing low returns, and warns that even patients with insurance are turning to the public system because of big out-of-pocket bills.